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Volume 1: Findings and Conclusions
Executive Summary of the Report of the Inquiry
3. The cause of BSE

  • Gathering of data about the extent of the spread of BSE was impeded in the first half of 1987 by an embargo within the SVS on making information about the new disease public. This should not have occurred.
  • By the end of 1987 Mr John Wilesmith, the Head of the CVL Epidemiology Department, had concluded that the cause of the reported cases of BSE was the consumption of meat and bone meal (MBM), which was made from animal carcasses and incorporated in cattle feed. This conclusion was correct. It had been reached with commendable speed.
  • The following provisional conclusions of Mr Wilesmith, which were generally accepted at the time as a basis for action, were reasonable but fallacious:
    - the cases identified between 1986 and 1988 were index (ie, first generation) cases of BSE;
    - the source of infection in the MBM was tissues derived from sheep infected with conventional scrapie;
    - the MBM had become infectious because rendering methods which had previously inactivated the conventional scrapie agent had been changed.
  • The cases of BSE identified between 1986 and 1988 were not index cases, nor were they the result of the transmission of scrapie. They were the consequences of recycling of cattle infected with BSE itself. The BSE agent was spread in MBM.
  • BSE probably originated from a novel source early in the 1970s, possibly a cow or other animal that developed disease as a consequence of a gene mutation. The origin of the disease will probably never be known with certainty.
  • The theory that BSE resulted from changes in rendering methods has no validity. Rendering methods have never been capable of completely inactivating TSEs.
  • The theory that BSE is caused by the application to cattle of organophosphorus pesticides is not viable, although there is a possibility that these can increase the susceptibility of cattle to BSE.
  • The theory that BSE is caused by an autoimmune reaction is not viable.
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